help with simple regex expression


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# 1  
help with simple regex expression

I am trying to grep the following line in a file using a bash shell:

(..)
admin1::14959::::::
(..)

It works with the following expression (as expected)

# cat file | grep ^[a-z0-9]*::
admin1::14959::::::

but it does not work with (not expected)

# cat /etc/shadow | grep ^[a-z0-9]+::

I assume the difference is the + vs. the *. According my
understanding the * matches the preceding character 0 or
more times and the + matches the preceding character 1
or more times. Therefore, the match should be in both cases
"admin1::"

I can not see my mistake. Any ideas ?
# 2  
That's an extended regexp. Use grep -E.
This User Gave Thanks to verdepollo For This Post:
# 3  
Or # cat /etc/shadow | egrep ^[a-z0-9]+::

Or # cat /etc/shadow | grep ^[a-z0-9][a-z0-9]*::
This User Gave Thanks to Chubler_XL For This Post:
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